For interior or exterior decoration of a surface, such as a building, a home or a vehicle, decorative polyvinyl chloride (PVC) based surface coverings are well known and widely used.
In particular, multilayer PVC coverings are well known which include a foamed support layer and a wear layer.
Habitually, such multilayer surface coverings are produced by gelling a foamable support layer, onto which a wear layer and possibly a decorative layer is applied. During this step, the blowing agents present in the composition of the support layer are activated and cause the support layer to foam, thereby creating numerous pores within the PVC, which results in a PVC foam.
A multilayer surface covering which includes a foamed support layer has special acoustic properties, properties that so-called “compact”, or non-foamed, surface coverings do not have.
It is generally accepted that the more the support layer is foamed, the better the acoustic properties of the surface covering. Thus, the acoustic performance characteristics of a foamed multilayer covering are habitually improved by increasing the thickness of the foam and by modifying the structure of the foam and particularly its density, i.e. by increasing its porosity. However, acoustic performance is generally improved at the expense of mechanical performance and conversely.
In addition, modification of the structure or the thickness of the PVC foam requires either the modification of the formulation of the composition of the support layer, or the modification of the operating conditions for the foaming of the support layer, and thus the operating conditions for the manufacture of the surface covering, or even both at the same time.
Thus, when one wants to produce coverings with different acoustic performance characteristics, the formulations and/or the operating conditions must be adapted to each specific covering produced, which requires numerous manipulations. Furthermore, these requirements are all the more important as the surface coverings are generally produced on a continuous production line. The production line must thus be stopped in order to make the necessary adjustments.